Oil-well borehole apparatus for natural-gamma radioactive logging type ASCRGN-86-A-I

The natural-gamma borehole radioactive apparatus records the global natural radioactivity of radioactive elements in the Uranium, Thorium and Potassium 40 series, as they are found in the lithological formations (layers) investigated in boreholes. It is designed for the geophysical investigation of wells, especially in the oil industry. It works at maximum depths of 6000 m, where the maximum admitted hydrostatic pressure is of 140 MPa. The technical characteristics of the apparatus are: - Dimensions: 86 mm (diameter) x 2000 mm(length)± 10%; - Operating external temperature range: -20 deg. C to +150 deg. C; - Maximum working time at +150 deg. C stationary: 30 min; - Surface power supply : 180 V / 50 - 60 Hz; - Maximum drained current: 60 mA; - Minimum detectable energy: 241 Am - 60 keV gamma-rays; - Own radiation background: (7±1) counts/s; - Minimum detectable activity at 300 mm distance from the apparatus: (140-280) ± 15% Bq for 226 Ra, (80-160) ±15% Bq for 232 Th, (2900-5700) ± 15% Bq for 40 K; - Output signal: electrical pulses with selectable positive or negative polarity, with amplitude of (12-15) V and duration between (20-50) μs. The counting rate minus background, with a 226 Ra calibrating source with the conventional true activity of (90,65 ± 10%) kBq, at 300 mm away from the scintillation crystal is: NRa = 238 ± 15% counts/s. (author)